[boost] How to add a library to the BoostBook Documentation Subset?

I have taken over the task of maintaining Boost Phoenix. I want to start expanding the documentation which already uses Quickbook. The BoostBook Documentation Subset here includes a lot of libraries but not Boost Phoenix. http://www.boost.org/doc/libs/1_55_0/doc/html/index.html How do I get Boost Phoenix added, and are there any requirements for the documentation which need to be observed? Thanks John Fletcher